1. Field of the Invention
The present invention relates to a light guide member for propagating light from an incident face toward an emitting face and an illuminating device having this light guide member.
2. Description of the Related Art
In a reflection type liquid crystal display device for performing a displaying operation with circumferential light as a light source, its brightness is influenced by the light amount of the circumferential light. Therefore, in an environment in which no sufficient circumferential light is obtained at the time of using in a dark place, etc., visibility of the display is extremely reduced. Therefore, a liquid crystal display device having a front light (face light emitting illuminating device) arranged on the front face side of the liquid crystal display unit (liquid crystal display element) of the reflection type, and used as an auxiliary light source is proposed. This liquid crystal display device having the front light is operated as the normal reflection type liquid crystal display device in an environment in which the circumferential light is sufficiently obtained in the outdoors during the daytime, etc. In this liquid crystal display device, the above front light is turned on and is used as a light source in accordance with necessity.
The front light has a light guide member forming a reflection face constructed by many fine grooves and prisms on its surface to uniformly illuminate the inside of the face of the liquid crystal display unit without irregularities. The wide face can be illuminated in uniform brightness by the action of such a reflection face even when a dot light source and a line light source are used as the light source. (For example, see Patent literature 1).
[Patent Literature 1]
JP-A-2000-180631
The utilization of the front light is being considered in various uses as an efficient illuminating means excellent in illumination ability. In consideration of such a present situation, the front light having a further suitable illumination ability in accordance with the shape and the utilization mode of an illuminated object has been desired.